ISSN:
1573-4943
Keywords:
Cathepsin D
;
kallistatin
;
antichymotrypsin
;
serpin
;
fluorogenic substrates
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract In the present paper, we demonstrate that α1-antichymotrypsin, a serpin with high inhibitory specificity toward cathepsin G, and kallistatin, a human serpin with high specificity toward tissue kallikrein, are digested by cathepsin D. α1-Antichymotrypsin was hydrolyzed essentially in the reactive center loop at L–S, A–L, or L–V bonds; kallistatin was split into small fragments, but we detected the cleavage at F–F and F–S bonds in its reactive center loop in the first 15 min of digestion. In contrast to α1-antichymotrypsin, kallistatin is irreversibly inactivated at pH 4.0. Synthetic internally quenched fluorescent peptides containing sequences similar to the reactive center loops of these serpins were hydrolyzed by cathepsin D. The peptides derived from kallistatin were hydrolyzed more efficiently, and particularly relevant was the high susceptibility of the substrates Abz-AIKFFSAQT-NRHILRFNRQ-EDDnp (K m = 0.08 μM, k cat = 2.4 s−1) and Abz-AIKFFSAQTNRQ-EDDnp (K m = 0.8 μM, k cat = 17.8 s−1), which were hydrolyzed at the F–F bond. Therefore, besides the description of a new class of very efficient internally quenched substrates for cathepsin D, we give evidence for the downregulation role of this proteinase on α1-antichymotrypsin and kallistatin. The acidification of extracellular milieu by tumor cells can result in activation of cathepsin D; as a consequence, kinins can be released, improving blood supply and leaving more cathepsin G available for the degradation of extracellular matrix.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1026432402259
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